1. Field of the Invention
The present invention relates to the field of light emitting transparent panels.
2. Prior Art
Light emitting transparent panels of various kinds are known in the art. See, for instance, U.S. Pat. Nos. 2,807,111, 3,338,730, 3,876,293, 4,043,636, 4,440,814, 5,536,558, 7,195,389 and 7,354,184. Such panels are normally illuminated at one or more places along an edge thereof by any of various light sources, including light emitting diodes. Most of the light from the light sources in a transparent panel with flat, parallel surfaces will have a shallow enough angle to continuously reflect from the surfaces of the panel and be confined within the panel. The light that does not have a sufficiently shallow angle will be emitted from the light panel very near the light source, and can be shaded to blackened out there. However, given a pattern of light extracting deformities or disruptions in the surface of the panel, some of the light within and passing along the panel will be interrupted and redirected outward from the surface of the panel and made visible to one looking at that surface of the panel. The light extracting deformities in the prior art have been formed by etching or molding. The size, shape and other characteristics of these deformities or disruptions may take various forms and have, in the prior art, been made of uniform size, or of increasing size with increasing distance from the light source.
One of the problems with the prior art methods of forming such light emitting panels has been the problem of obtaining uniform illumination of the pattern or patterns on the panels. In particular, even when using light emitting deformities on the panels that are of increasing size with increasing distance from the light source, the leading edge of such patterns, that is, the edge closest to the light source, tends to be brightest, with the illumination of the pattern decreasing from there across the pattern. It is these two combined effects, namely, the shadowing or shading as just described, coupled with general brightness which decreases with increase in distance from the light source that has been a major obstacle in the prior art, as the shadows caused by such shading appear to radiate from the light source and are immediately identifiable by an observer as not an intended part of the decorative pattern.